fix(host/windows): layout-correct keyboard injection - semantic vs positional VKs

First-party punktfunk clients send US-positional VKs (the physical key's
US-layout VK), GameStream/Moonlight clients send layout-semantic VKs
(Sunshine's model). The SendInput injector previously resolved everything
through the SYSTEM service's layout - on a German host that is the y/z swap
and u-umlaut-on-o-umlaut scramble. GameStream ingest now tags its key events
KEY_FLAG_SEMANTIC_VK (stripped from punktfunk/1 wire events so a network
client can't flip the convention); the injector maps semantic VKs under the
foreground app's layout and positional VKs through a fixed scancode table.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/punktfunk-host/src/punktfunk1.rs

@@ -1015,8 +1015,19 @@ async fn serve_session(
                 if rich_tx.send(rich).is_err() {
                     break;
                 }
-            } else if let Some(ev) = InputEvent::decode(&d) {
+            } else if let Some(mut ev) = InputEvent::decode(&d) {
                 input_count += 1;
+                // Wire hygiene: KEY_FLAG_SEMANTIC_VK is an in-process tag (GameStream ingest
+                // only) — strip it from network events so a client can't flip the host's
+                // key-decoding convention. Other kinds keep flags verbatim (MouseMoveAbs packs
+                // its reference extent there).
+                if matches!(
+                    ev.kind,
+                    punktfunk_core::input::InputKind::KeyDown
+                        | punktfunk_core::input::InputKind::KeyUp
+                ) {
+                    ev.flags &= !crate::inject::KEY_FLAG_SEMANTIC_VK;
+                }
                 if input_tx.send(ev).is_err() {
                     break;
                 }